[Mesa-users] How to calculate the neutrinos flux in different radii

[Rob Farmer]

Please keep replies on the mesa-users mailing list.

>It seems that the screened rate contains the information of density. Is my
understanding correct? Looking forward to your reply.

The screened_rates and raw_rates are density independent. They are set such
that a 2-body reaction would need multiplying by rho**2

>Y_1 and Y_2 are the mass fraction of elements with no unit,

You want the molar fractions not the mass fractions as you need the number
of particles involved in the reaction, that then also means you pick up a
factor of avogrado's constant.

Rob

On Thu, 10 Nov 2022 at 09:01, peter zhang <greatofdream at gmail.com> wrote:

> > Which lets you know what pre-factors you need. This is combined with ye
> and rho to get the density of electrons.
> Thanks for your clarification and I found an option `ye` in the
> `profile_columns.list`.
>
> > ! (0,1) for standard 2 body reaction.
> > ! (1,1) for 2 body electron captures
> Besides, I also wanted to make sure about my comprehesion of the unit of
> screened rate which seems different from the denfinition of `Astrophysical
> reaction rates` (<\sigma v>).
> + For standard  2 body reaction, the number of reaction is
> Rho*ScreenedRate*Y_1*Y_2, in which Y_1 and Y_2 are the mass fraction of
> elements with no unit, Rho is the density with unit g/(cm**3) , and the
> unit of ScreenedRate is mol/(g*s). The unit of above equation is
> mol/(cm**3).
> + For 2 body electron captures , the number of reaction is
> Ye*Rho*ScreenedRate*Y_1, in which Y_1 and Ye are with no unit, Rho is with
> unit g/(cm**3) , and the unit of ScreenedRate is still mol/(g*s). The unit
> of above equation is mol/(cm**3).
> It seems that the screened rate contains the information of density. Is my
> understanding correct? Looking forward to your reply.
>
> I am grateful to your help!
> Peter
>
>
> Rob Farmer <robert.j.farmer37 at gmail.com> 于2022年11月9日周三 17:14写道：
>
>> Hi,
>> Thanks for sharing your run_star_extras.f90
>>
>> In the next release there will be history and profile column outputs for
>> the nuclear and neutrino energy losses per reaction. In the current RC1
>> there are the options:
>>
>> !add_raw_rates ! raw reaction rates, reactions/second
>> !add_screened_rates ! screened reaction rates reactions/second
>> !add_eps_nuc_rates ! Nuclear energy (minus neutrino losses) released erg/s
>> !add_eps_neu_rates ! Neutrino losses erg/s
>>
>> But these have some bugs in the accounting in the RC1 so I would wait
>> until we release the next version of MESA where we should have fixed these
>> issues.
>>
>> >*I cannot find an option or variable to output the number density of
>> electrons*
>>
>> If you look in rates_def.f90:
>>
>> integer, pointer :: reaction_ye_rho_exponents(:,:)=>NULL() !
>> (2,rates_reaction_id_max)
>>             ! multiply T dependent rate by Ye^a(i) * Rho^b(i)
>>             ! reaction_ye_rho_coeffs(1,i) is a(i)
>>             ! reaction_ye_rho_coeffs(2,i) is b(i)
>>             ! (0,0) for photodisintegrations and decays
>>             ! (0,1) for standard 2 body reactions
>>             ! (0,2) for 3 body reactions such as triple alpha
>>             ! (1,1) for 2 body electron captures
>>             ! (1,2) for 3 body electron captures (e.g., pep)
>>
>> Which lets you know what pre-factors you need. This is combined with ye
>> and rho to get the density of electrons.
>>
>> Rob
>>
>>
>> On Wed, 9 Nov 2022 at 05:27, peter zhang via Mesa-users <
>> mesa-users at lists.mesastar.org> wrote:
>>
>>> Greetings mesa-users,
>>> I am using MESA  to calculate the flux of different types of neutrinos
>>> in different radii. There do not exist similar options in
>>> `profile_columns.list`.  I try to calculate the number of reactions of
>>> different types to represent the flux of different types of neutrinos.
>>>
>>> I have extracted the screened rates in `run_star_extras.f90`, which is
>>> attached in* the *attachment. The mass fractions of different isotopes
>>> are also acquired from the model file. The unit of screened rates is
>>> related to the number of reactants which has referred in the `net_def.f90`:
>>> ```
>>> ! so for a 2-body reaction, there are 2 Y factors, each with units
>>> [moles/gram]
>>> ! and the rate_screened units for such a reaction are
>>> [grams/(mole-sec)],
>>> ! which when multiplied by [moles/gram]^2 gives the same units as dydt.
>>> ```
>>>
>>> For example, the number (/cm3/s) of  reaction `pep`(p + e^- + p -> H2
>>> +nu_e), which is a 3-body reaction, is the product of screened rate, the
>>> molar density of p, and* the molar density of electrons*. The number
>>> density of electrons is needed but *I cannot find an option or variable
>>> to output the number density of electrons. Maybe there exist simpler
>>> methods or I misunderstand something.* Any help or clarification you
>>> could provide would be greatly appreciated.
>>>
>>> I am looking forward to your reply.
>>>
>>> Thank you for your time,
>>>
>>> Peter
>>> _______________________________________________
>>> mesa-users at lists.mesastar.org
>>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>>
>>>
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